Many types of articles are currently manufactured from one or more webs of materials. Methods of making articles from one or more webs of material include, but are not limited to: processes for making empty bags; processes for making and filling bags; and, processes for making disposable absorbent articles. During manufacture, the web(s) of material may be moved through the manufacturing process, and may have various tasks performed on the same to produce the final product.
Methods of making disposable absorbent articles are described in U.S. Pat. Nos. 8,145,343 B2 and 8,145,344 B2, both to DeBruler, et al; and U.S. Pat. No. 8,168,254 B2, Dovertie, et al. Methods and apparatuses for making bags and attaching features to the same are described in the patent literature, including in the following patent publications: U.S. Pat. No. 5,000,725, Bauknecht; U.S. Pat. No. 5,292,299, Anderson, et al.; U.S. Pat. Nos. 5,518,559 and 5,660,674 to Saindon, et al.; U.S. Pat. No. 5,861,078, Huben, et al.; Canadian Patent Application 2,173,931; U.S. Pat. No. 6,251,209 B1; and U.S. Pat. No. 7,175,582 B2, Owen. Machines for making bags and attaching features to the same are also commercially available. One such machine is the NEWTON 400® intermittent motion packaging machine sold by UVA Packaging, Richmond Va., U.S.A.
The search for improved methods and apparatuses for accurately performing multiple tasks on moving webs of material during manufacturing processes has, however, continued. For example, the film used to make pet food bags is typically a composite of two laminates, with a first laminate comprising the printing, and a second laminate providing the main body and strength to the bag. The printed laminate comprises repeating graphics, associated with each bag to be made, and each of them comprises at least one registration mark to signal to the equipment when to perform certain tasks, like placing a zipper or other features, forming a seal and making a cut between bags. If only one registration mark is used per bag, then the distance between registration marks is a measure of the bag length for the bags next to the registration marks. As this film is presented to the bag making machine, any variation in the distance between registration marks can cause problems in accurately performing those tasks. The variation in the distance between registration marks or otherwise variation in the bag length can be introduced in a number of ways including, but not limited to: (1) variations in the printing of the films used to make the bags; (2) variations in winding of the films; (3) stretching of the films during manufacture; (4) variations in length due to splicing of film rolls at the film manufacturer; (5) variations in length due to splicing of the film rolls at the bag manufacturing plant; (6) variations that may be inherent in the machine, such as due to wear; and (7) creep in the wound roll due to storage or winding conditions.
Therefore, there is a need for an improved method and apparatus for accurately performing multiple tasks on a moving web of material. For example, it is desirable to improve the accuracy of placing features such as zippers on bags, and making cuts that are well aligned to graphics on the bag material. Such improvements can result in significant savings in avoiding creating defective bags of products due to improper seals or graphics issues.